Electrically heated cooking appliance

ABSTRACT

An electrically heated cooling appliance of the type having a removable, probe-type, thermostatic temperature control device and comprising a base having an upper surface to be heated and an electric heater means on the underside of the base having terminal ends protruding therefrom. Means integrally formed on the underside of the base is provided to define only a portion of a temperature sensing zone. The remainder of this zone wherein the probe is received is defined by bracket means secured to the underside of said base which bracket means also includes means supporting a pair of terminal connectors for engagement with suitable connectors defined on the removable probe-type temperature-responsive, control device when the latter is applied by inserting the probe into the temperature sensing zone.

United States Patent 1151 3,681,568 Schaefer 1 Aug. 1, 1972 [s41 ELECTRICALLY HEATED COOKING 2,926,230 2/1960 Foster ..219/435 x APPLIANCE 1 2,952,764 9/1960 Minarni; ..219/432 3,007,029 10/1961 Levine, ..219/436 [72] Invent @fig' schaefe" wauwamsa 3,025,378 3/1962 Sadell ..219 449 I 3,037,107 5/1962 Clark ..219/439 1 h 051 r 1 M'l v A [73] Ass'gnee fl f' ac FOREIGN PATENTS-0R APPLICATIONS 22 Filed: Dec. 15 1971 915,010 7/1954 Germany ..219/449 Appl. No.: 208,429

Related US. Application Data Continuation of Ser. No. 41,239, May' 28, 1970, abandoned.

US. Cl. ..219/432, 99/325, 99/447 219/430, 219/433, 219/435, 219/436,

Int. Cl ..F27d 11/02 Field of Search ..99/422, 447, 325, 326; 219/250-252, 429, 430, 432-436, 438, 439,

References Cited UNITED STATES PATENTS 5/1938 Cross ..219/436 9/1942 Barnes ..219/252 12/1942 Potsdam ..219/449 12/1943 Price ..219/252 8/1954 Koci ..219/435 X Primary Examiner-Volodymyr Y. Mayewsky Attorney-George R. Clark 57 ABSTRACT An electrically heated cooling appliance of the type having a removable, probe-type, thermostatic temperature control device and comprising a base having an upper surface to be heated and an electric heater 9 11 Claims, 9 Drawing Figures ELECTRICALLY HEATED COOKING APPLIANCE This is a continuation of application Ser. No. 41,239, filed May 28, 1970 now abandoned.

The. present invention relates to a new and improved electrically heated cooking appliance of the type having a removable, temperature-responsive, probe-type control device for controlling the electric current supplied to heater means in the appliance base.

In recent years, fondue pots have become increasingly popular cooking devices, and in this type of appliance it is desirable to have an extremely accurate temperature control so that the cooking oil or sauce or other material in the fondue pot does not become overheated and burn or spatter out or boil over onto the table surface, yet remains high enough in temperature to properly cook the food.

Another problem encountered with fondue pots is the fact that the quantity of oil, sauce, foods, or the like, initially present in the pot before the meal-commences gradually decreases as the meal proceeds, and a natural tendency to overheat the remaining smaller volume of oil, sauce or the like, during the latter stages of the meal must be prevented.

Another difficulty encountered with fondue pot cookery is that the heating load is continuously changed as fresh, relatively cold items to be cooked are deposited in the oil or sauce and cooked, and relatively hot items are removed from the boiling oil, sauce or the like on a random basis.

Accordingly, temperature control of the cooking medium in a fondue pot should be capable of reacting the present invention are accomplished in a new and improved electrically heating cooking appliance including a base assembly having an upper surface heated and maintained at a selected temperature level. The base assembly includes a heating tray portion formed with electrical heater means on the underside, preferably cast into or embedded in the base, and terminal ends of the electric heaterprotrude outwardly of the base structure at spaced apart locations. Wall means are integrally formed on the underside of the heating tray portion defining only a portion of a temrapidly to wide ranges and changes of heat load in order to prevent overcooling or overheating of the oil described which is capable of overcoming the aforementioned difficulties and problems of prior art open flame heated devices.

Another object of the present invention is to provide a new and improved electrically heated cooking appliance.

Still another object of the present invention resides in the provision of a new and improved electrically heated cooking appliance which is capable of maintaining a relatively constant temperature of a quantity of cooking medium or food even though the cooking conditions vary widely and at random. In this connection the fondue pot may be used for boiling water as well as heating oils, sauces, cheeses and other cooking media.

A further object of the present invention is to provide a new and improved electrically heated fondue pot especially adapted for conveniently cooking food at the table.

Another object of the present invention is to provide a new and improved electrically heated appliance of the character described employing improved temperature control means in order to prevent overcooling or overheating of the cooking fluid or the like.

Another object of the present invention is to provide a new and improved electrically heated cooking appliance having novel means for effectively maintaining perature probe receiving passageway which is open at least at the end adjacent the periphery of the base. A bracket is secured to the wall means to complete the probe receiving passage and thereby to define a temperature sensing zone. The bracket includes an integral support flange which extends transversely of the passageway. A pair of terminal pins are supported on the flange and are electrically connected to the terminal ends of the heater which are spaced on opposite sides of the passageway with the longitudinal axes of the terminal pins and the passageway arranged in spaced parallel relationship. A removable, temperature-responsive, probe-type control device is provided for controlling electrical current supplied to the heater means in order to maintain a selected upper surface temperature of the base. The control device includes an elongated temperature-sensitive probe which is insertable into the passageway defined partly by means integral with the base and partly by the bracket. The

probe transfers heat from the temperature sensing zone to a thermostatically controlled switch means which opens and closes in response to the temperature sensed by the probe to energize and de-energize the heater means.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawings, in which:

FIG. 1 is a front perspective view of an electrically heated fondue pot constructed in accordance with the present invention with the removable probe in temperature controlling position; 7 FIG. 2 is a vertical, sectional view taken substantially along line 2-2 of FIG. 1 with the removable probe shown in phantom;

FIG. 3 is a fragmentary, front elevational view looking in the direction of the arrows 3-3 of FIG. 2;

FIG. 4 is a plan view of the underside'of the heating tray portion of the fondue pot before assembly of the bracket therewith;

FIG. 5 is an enlarged fragmentary view of the portion of the underside of the heating tray portion adjacent the area where the temperature sensing zone is defined, but unlike FIG. 4 has the bracket assembled therewith to complete the temperature sensing zone and permit association therewith of a removable probe-type thermostatic control device; I

FIG. 6 is a fragmentary front elevational view looking substantially in the direction of the arrows 6-6 of FIG. 5;

FIG. 7 is an exploded view in vertical section of the I fondue pot with the removable kettle not sectioned;

FIG. 8 is an enlarged fragmentary sectional view through the removable temperature responsive control device of the fonduepot taken substantially along line 8-8 of FIG. 2 assuming FIG. 2 shows the complete structure; and

FIG. 9 is an enlarged, fragmentary, horizontal sectional view taken substantially along line 9-9 of FIG. 8 assuming that FIG. 8 shows the complete structure.

Referring now more particularly to the drawings, there is illustrated a new and improved electrically heated cooking appliance comprising a fondue pot generally indicated at 10 and constructed in accordance with the features of the present invention. The fondue pot 10 essentially comprises a separate removable cooking vessel or kettle 11 for holding the quantity of cooking fluid, such as oil, water, sauce, etc.,

or foods, such as cheeses, chocolate, etc., in which food items are cooked, a supporting base assembly 12 for the removable kettle l1, and a removable thermostatic probe'type temperature responsive control device 13 for regulating and controlling the heating of a portion of the base assembly 12 as described in detail hereinafter.

The kettle 11, which is an open top kettle, is adapted to contain a relatively large quantity of cooking medium, usually oil of some sort, and includes a flat circular bottom 11a and an annular, upstanding sidewall 11b which tapers inwardly towards the open top to help prevent the spillage or splashing of hot cooking media or foods outside of the kettle as food items are introduced or taken from the kettle. Preferably the kettle 11 is formed of a good conductor of heat, such as aluminum, and may have the interior thereof coated with a suitable coating to simplify cleaning thereof. The kettle 11 is provided with a lifting handle 14 so that the vessel and its contents may be easily lifted from the support base structure 12 when desired. In accordance with the present invention, several kettles 11 may be employed with one supporting base assembly 12 and control device 13. For example, a cheese fondue may be heated and served in a first kettle 11 as an appetizer. Then a second kettle 11 may be used for a meat fondue as the main course and finally a third kettle 11 may be used for a dessert fondue. Thus one heating device may be used for several courses of a meal using a plurality of kettles ll.

The assembly 12 of the present invention includes a heated shallow panlike heating tray 15 and insulating supporting means 16 and 17, respectively. The tray 15 is illustrated as having a fiat circular bottom 15a, and

an upwardlycurved or dished peripheral sidewall 15b. The tray is preferably cast from ametal of good heat conductivity.- The upper edge of the curved sidewall 15b is terminated in a horizontally outwardly extending upper flange or rim 150. The lower portion of the kettle l1 and the tray 15 are dimensioned and shaped'to accommodate one another so that good conductive heat transfer between the upper surface of the bottom 15a of tray 15 and the lower surface of the bottom 11a of the kettle 1 1 is established when the vessel is in cooking position, as best shown in FIGS. 1 and 2 of the drawings. The close intimate heat engaging contact between portions 11a and 15a is clearly illustrated in FIG. 2 of the drawings. A slight amount of clearance is provided between the upwardly curved sidewall portion 15b of the tray 15 and the adjacent wall portion 11b of the kettle 11 to provide for difierences in thermal expansion and still permit easy placement or removal of the kettle 11 relative to the tray 15. It is important that the tray 15' has a contour conforming to that of one or more removable kettles 11 to provide for maximum heat transfer.

For the purpose of heating the tray 15, an electrical heating element 18 of the conventional sheathed type is provided. As illustrated best in FIG. 4 of the drawings this heating element 18 is of C-shape and, is illustrated as being cast into or embedded in the metal defining tray 15 and within a downwardly projecting rib structure 15d. Specifically the heating element 18 includes a resistance heater wire 19 coaxially aligned within an outer tubular sheath 20 and electrically insulated therefrom by a conventional filler material preferably comprising compacted magnesium oxide granules 21 (FIGS. 2 and 8) which have good heat transfer capability. As best shown in FIGS. 4, 5 and 8 of the drawings, the C-shaped heating element 18 terminates in downwardly projecting terminal portions 19a and In order to define a temperature sensing zone for the probe of the removable probe-type control 13, the heated tray 15 is provided on its underside with an integrally formed downwardly projecting wall structure including two spaced parallel walls 15a and 15f which are joined at the under surface of the tray 15 by a curved surface 15g. The space between the walls l5e and 15f and bounded by said curved surface defines a probe receiving passageway 22 open at the bottom and open at each end. The open bottom is adapted to be closed, as described hereinafter, and when closed there is defined the tubular passageway 22 comprising a temperature sensing zone. The wall structure comprising walls 15c and 15f includes integral projections best shown in FIG. 4 of the drawings having tapped openings 23 therein to accommodate fastening means described hereinafter. The longitudinal axis of the passageway 22 bisect the space between terminals 19a and 19b and the probe entrance opening to the passageway 22 is adjacent the periphery of tray 15.

It will be appreciated that the tray 15 described above can be manufactured at a substantially lower cost than similar heating devices by virtue of the downwardly directed terminal portions 19a and 19b and the passageway 22 open at the bottom. No side coring for the mold would be required thus reducing tooling costs and machining operations are not required with respect to the means defining the temperature sensing zone.

To aid in firmly securing the heated tray to the insulating supporting means 16 and 17 the former is provided with an integral downwardly projecting centrally located tubular member 15h which is internally threaded for a purpose described in greater detail hereinafter. In addition a plurality of depending projections 15j are provided on the underside of tray 15 (FIG. 4) for further securing the tray 15 and supporting means 16 and 17 together as the support base structure 12.

For the purpose of completing the tubular passageway 22, defining the temperature sensing zone there is provided a T-shaped bracket 24 defining both a combined terminal support member and closure plate. The bracket 24 comprises a horizontal leg or closure plate portion 24a defining the leg of the T and a vertically disposed plate portion 24b defining the head of the T. The bracket 24 is secured to the heated tray 15 by a plurality of fastening means such as cap screws 25 threadedly engaged in the tapped openings 23 of the wall structure including walls l5e and 15f, thereby completing the tubular passageway 22. The plate portion 24b includes an integral forwardly projecting, stiffening lip or rib 240, as best shown in FIGS. 5, 6 and 7 of the drawings.

As best shown in FIGS. 3, 6 and 9 of the drawings the flange 24b is a terminal supporting flange and supports in electrically insulated relationship a pair of spaced male type terminal pins 26, one disposed on either side of the longitudinal axis of passageway 22. These pins are adapted to make electrical connection in the conventional manner with cooperating female type contacts associated with the removable probe type unit 13. To support the terminals in insulated relationship from bracket 24 and as best shown in FIG. 9 of the drawings, the terminal pins 26 are provided with threaded portions 26a intermediate the ends and an annular flange or shoulder 26b adjacent a short inner end portion 26c thereof. The threaded body portions 26a of the terminal pins project through suitable apertures 27 formed in the plate portion 24b. The terminal pins are insulated from the plate portion 24b by a plurality of insulating sleeves 28, and insulatingwashers 29 and are positively clamped in place by locknuts 30 and washers 31.

It will be obvious that bracket 24 performs'a dual function of forming the bottom closure for the probe receiving passageway 22 and also supporting the male terminal pins 26. Moreover bracket 24 may be a low cost stamping which establishes the spacing between terminal pins 26. With this arrangement the spacing between the terminal pins 26 can be chosen as desired and accurate spacing is assured. This eliminates the problems caused by casting stresses requiring large tolerances in the spacing of the terminal pins where they are mere extensions of the cast-in heating element as is the conventional practice.

In order to complete the electrical circuit between the heating element 18 and terminal pins 26 short jumper wires 32a and 32b are provided. The jumper wire 32 preferably has one end spot welded to heater terminal 19a and the other end similarly connected to one of the terminals 26 as shown in FIGS. 5 and 8 of the drawings. Similarly jumper wire 32b interconnects heater terminal 19b with the other terminal 26.

Considering now the two part insulating supporting means 16 and 17, each is formed of a suitable moldable material which is strong, light in weight, and a good heat insulator as well as an electrical insulator. The portion 16 might be characterized as an insulating tray to substantially enclose heating tray 15 and associated parts while the portion 17 might be characterized as a leg structure. The reason for a two part supporting means is to simplify manufacture and assembly operations and also to permit different moldable materials to be used if desired. To insure stable support, the portion 17 comprises three integral spaced legs 17a, each leg having a rivetlike cushionfoot 33 on the surface engaging end thereof. The upper ends of the legs 17a join into a generally circular body portion 17b having a centrally positioned, upstanding, stepped diameter, hollow cylindrical sleeve 17c projecting upwardly. therefrom and designed to abut the lower end of the tubular member 15a depending from heated tray 15 (FIG. 2). The sleeve has a passageway 34 therein terminating in a large diameter lower end portion 34a. With this arrangement a suitable fastening means such as screw 35 engaging the internally threaded portion of tubular member 15h secures the leg structure 17 to the heated tray 15. Removal of this single screw 35 permits ready disassembly of the parts 16 and l7'for cleaning purposes if desired.

The insulating tray 16 comprises a shallow panlike portion 16a adapted to receive therein in spaced relationship the heating tray 15, as best shown in FIG. 2 of the drawings. Thus the depending projections 15] of the heating tray 15 engage the insulating tray 16 to determine the spacing between trays 15 and 16. Depending from the bottom of insulating tray 16 is an annular projection or ring 16b receivable in a cooperating annular groove 36 defined in the circular body portion 17b of leg structure 17. The ring 16b and groove 36 position the parts 16 and 17 in a predetermined concentric relationship and they are secured together as a unitary structure by screws 37 extending through openings 38 (FIG. 7) in insulating tray 16 engageable with tapped openings 39 in the central portion 170 of leg structure 17 (FIGS. 2 and 7).

Although the screw 35 will hold the leg structure 17 and the insulating tray 16, secured thereto by screws 37, assembled to heating tray 15, without more, relative rotation of the insulating support means 16 and 17 and heating tray 15 could occur. To prevent this the inside of pan portion 16a is provided with a cylindrical recess 40 to accommodate therein a depending cylindrical projection 15k from heating tray 15 (FIGS. 2, 4 and 7). With this arrangement the heating tray 15 and insulating support means 16 and 17 are secured together for ready disassembly as if comprising an integral structure. Moreover the insulating tray portion 16a fully encloses the entire underside of the heating tray 15 thereby to protect the user from inadvertent contact with the hot tray but also to protect the surface upon which the fondue pot 10 is supported from radiant as well as conductive heat.

For the purpose of ensuring that the insulating supportmeans remains relatively cool it is, of course, as clearly illustrated, spaced from the heating tray 15.

Furthermore, the circular base portion 17b of the leg structure 17 is provided with ventilating apertures 41 and the panlike portion 16a of the insulating tray 16 is provided with an enlarged central opening 42 (FIG. 7). Thus air can freely circulate between the underside of the heating tray and the insulating support means 16 and 17. In FIG. 2 the annular space 43 between members l5 and 16 is clearly shown.

In order to define a suitable receptacle for the projecting terminalpins 26 and to receive the removable probe unit 13, the insulating tray 16 includes an integral boxlike portion 16c adjacent where the terminal pins 26 are located thereby forming a housing or enclosure around bracket 24. The projection 16c defines an outwardly opening recess 44 of generally rectangular configuration (FIG. 3) adapted to receive therein a portion of the thermostatically controlled probe type device 13. As-best shown in FIGS. 7 and 8, the rear of recess 44 is defined by a wall 16d having a central opening 45 therein in line with the probe receiving passageway 22. In addition, the wall 16d is provided with a pair of terminal pin receiving openings 46 on opposite sides of the center opening 45 to accommodate the terminal pins 26 which project outwardly from the I bracket 24 into recess 44. The rectangular recess 41 is dimensioned to removably receive therein the probe- 'type temperature control device 13 in the conventional manner. The details of the device 13 form no part of the present invention but may be of conventional construction. As illustrated in FIGS. 1 and 8 of the drawings it comprises a housing 48 having a rear wall 48a from which projects the conventional probe 49 receivable within the temperature sensing zone defined by the passageway 22 when the control device 13 is received in the recess 44.

Mounted within housing 48 are female type terminals 51 mounted in spaced relationship and adapted to electrically engage the terminal pins 26 in the manner indicated in FIGS. 8 and 9 of the drawings. Suitable openings 52 are defined in rear wall 48a of housing 48 whereby terminal pins 26 may extend through these openings electrically to engage the cooperating female terminals 51. A suitable power cord 53 (FIG. 1) supplies power to female terminals 51 through a thermostatically controlled switch comprising contacts 54a and 54b (FIG. 8). An adjustable knob 55 is provided mounted on the forward portion of housing 48 to permit the user to select a desired temperature to be maintained for the liquid in kettle 11. A typical probe-type control for the temperature-responsive control device 13 is shown in US. Pat. No. 3,083,283. The temperature-sensitive control device 13 is bodily removable from the recess 44 and the probe 49 is movable along the longitudinal axis thereof into and out of passageway 22 in the heating tray 15. Simultaneously with this movement of probe 49 the electrical circuit between terminal pins 26 and female type terminals 51 is made or broken.

By employing the removable control the fondue pot can readily be cleaned although submersion of the base assembly 12 is not normally contemplated. Spills and spatters can be easily sponged off without being concerned about the removable probe unit 13. Moreover the base unit can readily be disassembled for a more thorough cleaning by removal of a single screw 35.

While there has been shown and described a particular embodiment of the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the invention in its broader aspects, and it is, therefore, contemplated in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desiredto be secured by Letters Patent of the United States is:

1. An electrically heated cooking appliance comprising a heating tray having a flat circular bottom portion and an upwardly curved peripheral side wall extending only a short distance above said flat bottom portion, said heating tray being formed of a good heat conducting material, an electrical heating element in intimate heat exchange relationship with said heating tray, a removable vessel having a side wall of an extent to define a container having a depth several times greater than the depth of said heating tray, said removable vessel having a bottom and a small section of the lower portion of the side wall of said vessel contoured to fit in good heat conducting relationship within said heating tray, said vessel having a circular flat-bottom in heat exchange engagement with said bottom portion and a portion of the side wall of said vessel being in heat exchange relationship with said curved peripheral side wall, a temperature sensing control device positioned closely adjacent to said heating tray and responsive to the temperature of said heating tray for connecting said heating element to an electrical power source and for maintaining said heating tray at a constant preselected temperature, and an insulating support tray of shallow pan-like configuration mounted in spaced relationship with said heating tray to provide an annular passageway between the adjacent open tops ofsaid heating tray and said support tray, and fastening means for securing said trays in said spaced relationship.

2. The cooking appliance of claim 1 wherein the side wall of said removable vessel is tapered inwardly toward the top thereof to prevent spillage or splashing of liquid placed in said vessel.

3. The cooking appliance of claim 1 wherein a ventilating opening is provided in said insulating support tray to pennit the flow of air through said opening and said annular passageway.

4. An electrically heated cooking appliance comprising a heating tray having a flat circular bottom portion and an upwardly curved .peripheral side wall, said tray being formed of a good heat conducting material and having an electrical heating element secured to the underside of said bottom portion, a removable vessel having bottom and side walls contoured to fit into good heat conducting relation to said tray, said vessel having a circular flat bottom in engagement with said bottom portion and curved side walls which are positioned in closely spaced relation to said tray side walls, said tray including a pair of parallel downwardly depending side walls integrally formed on the bottom thereof defining a temperature sensing zone therebetween, closing means extending across the ends of said depending side walls to enclose all but the ends of said temperature sensing zone, a detachable temperature sensing and control device for connecting said heating element to an electrical power source, said sensing and control device being positioned in good heat transfer relation with the bottom of said tray and extending into said zone between said side walls to control the temperature of said vessel.

5. The appliance of claim 4 wherein said vessel is formed with inwardly sloping walls to provide a top opening which is smaller in diameter than said circular flat bottom.

6. The appliance of claim 4 wherein said tray is provided with an insulating supporting base detachably secured to the underside of said tray, said base having legs for supporting said appliance on a horizontal surface, said base shielding said surface from radiation from said element and tray.

7. An electrically heated cooking appliance comprising means defining a heating surface, an electrical heating element in heat exchange relationship with said first mentioned means, downwardly depending wall means integrally formed with said first mentioned means including a pair of spaced parallel walls defining a temperature sensing zone therebetween and including lower edges, a bracket including a wall portion secured to said first mentioned means and engaging said lower edges of said parallel walls remote from said first mentioned means further to enclose said temperature sensing zone thereby defining an elongated tubular passageway between said walls and above said wall portion of said bracket, a pair of terminal connectors supported by said bracket in spaced parallel relationship with the longitudinal axis of said passageway, means for electrically connecting said heating element to said ter minal connectors, and a probe type removable temperature responsive control means having a projecting probe receivable in said passageway and terminals engageable with said terminal connectors when said probe is within said temperature sensing zone.

8. The appliance of claim 7 including insulating support means for said means defining a heating surface including an outwardly opening cavity defined thereby for removably receiving said probe type control means, said cavity having an apertured inside wall providing access to said passageway and terminal connectors.

9. The appliance of claim 7 wherein an insulating support is secured to said means defining a heating surmeans and said base structure, whereby upon removal of said control means the parts of said appliance may readily be cleaned.

10. An electrically heated cooking appliance comprising a heating tray having a flat circular bottom portion and an upwardly curved peripheral side wall extending only a short distance above said flat bottom portion, said heating tray being formed of a good heat conducting material, an electrical heating element in intimate heat exchange relationship with said heating tray, a removable vessel having a side wall tapering inwardly to prevent spillage or splashing of liquid placed in said vessel, the side wall of said vessel being of such extent as to define a container having a depth several times greater than the depth of saidheating tray, said removable vessel having a bottom and a small section fthl io ft esidew lofsaidv elc our d "t hlfi g o d eat con ucting ref tionshi p within said heating tray, said vessel having a circular flat bottom in heat exchange engagement with said bottom portion and a portion of the side wall of said vessel being in heat exchange relationship with said curved peripheral side wall, a temperature sensing control device positioned closely adjacent to said-heating tray and responsive to the temperature of said heating tray for connecting said heating element to an electrical power source and for maintaining said heating tray'at a constant preselected temperature, and an insulating 

1. An electrically heated cooking appliance comprising a heating tray having a flat circular bottom portion and an upwardly curved peripheral side wall extending only a short distance above said flat bottom portion, said heating tray being formed of a good heat conducting material, an electrical heating element in intimate heat exchange relationship with said heating tray, a removable vessel having a side wall of an extent to define a container having a depth several times greater than the depth of said heating tray, said removable vessel having a bottom and a small section of the lower portion of the side wall of said vessel contoured to fit in good heat conducting relationship within said heating tray, said vessel having a circular flat bottom in heat exchange engagement with said bottom portion and a portion of the side wall of said vessel being in heat exchange relationship with said curved peripheral side wall, a temperature sensing control device positioned closely adjacent to said heating tray and responsive to the temperature of said heating tray for connecting said heating element to an electrical power source and for maintaining said heating tray at a constant preselected temperature, and an insulating support tray of shallow pan-like configuration mounted in spaced relationship with said heating tray to provide an annular passageway between the adjacent open tops of said heating tray and said support tray, and fastening means for securing said trays in said spaced relationship.
 2. The cooking appliance of claim 1 wherein the side wall of said removable vessel is tapered inwardly toward the top thereof to prevent spillage or splashing of liquid placed in said vessel.
 3. The cooking appliance of claim 1 wherein a ventilating opening is provided in said insulating support tray to permit the flow of air through said opening and said annular passageway.
 4. An electrically heated cooking appliance comprising a heating tray having a flat circular bottom portion and an upwardly curved peripheral side wall, said tray being formed of a good heat conducting material and having an electrical heating element secured to the underside of said bottom portion, a removable vessel having bottom and side walls contoured to fit into good heat conducting relation to said tray, said vessel having a circular flat bottom in engagement with said bottom portion and curved side walls which are positioned in closely spaced relation to said tray side walls, said tray including a pair of parallel downwardly depending side walls integrally formed on the bottom thereof defining a temperature sensing zone therebetween, closing means extending across the ends of said depending side walls to enclose all but the ends of said temperature sensing zone, a detachable temperature sensing and control device for connecting said heating element to an electrical power source, said sensing and control device being positioned in good heat transfer relation with the bottom of said tray and extending into said zone between said side walls to control the temperature of said vessel.
 5. The appliance of claim 4 wherein said vessel is formed with inwardly sloping walls to provide a top opening which is smaller in diameter than said circular flat bottom.
 6. The appliance of claim 4 wherein said tray is provided with an insulating supporting base detachably secured to the underside of said tray, said base having legs for supporting said appliance on a horizontal surface, said base shielding said surface from radiation from said element and tray.
 7. An electrically heated cooking appliance comprising means defining a heating surface, an electrical heating element in heat exchange relationship with said first mentioned means, downwardly depending wall means integrally formed with said first mentioned means including a pair of spaced parallel walls defining a temperature sensing zone therebetween and including lower edges, a bracket including a wall portion secured to said first mentioned means and engaging said lower edges of said parallel walls remote from said first mentioned means further to enclose said temperature sensing zone thereby defining an elongated tubular passageway between said walls and above said wall portion of said bracket, a pair of terminal connectors supported by said bracket in spaced parallel relationship with the longitudinal axis of said passageway, means for electrically connecting said heating element to said terminal connectors, and a probe type removable temperature responsive control means having a projecting probe receivable in said passageway and terminals engageable with said terminal connectors when said probe is within said temperature sensing zone.
 8. The appliance of claim 7 including insulating support means for said means defining a heating surface including an outwardly opening cavity defined thereby for removably receiving said probe type control means, said cavity having an apertured inside wall providing access to said passageway and terminal connectors.
 9. The appliance of claim 7 wherein an insulating support is secured to said means defining a heating surface, securing means for fastening said first mentioned means and said insulating support together effectively to provide a unitary structure, said securing means permitting ready disassembly of said first mentioned means and said base structure, whereby upon removal of said control means the parts of said appliance may readily be cleaned.
 10. An electrically heated cooking appliance comprising a heating tray having a flat circular bottom portion and an upwardly curved peripheral side wall extending only a short distance above said flat bottom portion, said heating tray being formed of a good heat conducting material, an electrical heating element in intimate heat exchange relationship with said heating tray, a removable vessel having a side wall tapering inwardly to prevent spillage or splashing of liquid placed in said vessel, the side wall of said vessel being of such extent as to define a container having a depth several times greater than the depth of said heating tray, said removable vessel having a bottom and a small section of the Lower portion of the side wall of said vessel contoured to fit in good heat conducting relationship within said heating tray, said vessel having a circular flat bottom in heat exchange engagement with said bottom portion and a portion of the side wall of said vessel being in heat exchange relationship with said curved peripheral side wall, a temperature sensing control device positioned closely adjacent to said heating tray and responsive to the temperature of said heating tray for connecting said heating element to an electrical power source and for maintaining said heating tray at a constant preselected temperature, and an insulating support tray of shallow pan-like configuration mounted in spaced relationship with said heating tray to provide an annular passageway between the adjacent open tops of said heating tray and said support tray, and securing means including a single threaded fastening means for securing said trays in said spaced relationship.
 11. The cooking appliance of claim 10 wherein first cooperating support means projecting from the bottom of said heating tray and second cooperating support means projecting from said insulating support tray maintain a predetermined spaced relationship between said trays to define said annular passageway. 